You're hot then you're cold

After my freshman year of my undergraduate degree, I spent two years living in Taipei, Taiwan as a missionary for my church. During that time I had a lot of interesting experiences. I ate everything from cow tongue and chicken feet to stinky tofu. Another one of my experiences there was ordering food at McDonalds. As a treat to myself after a hard days work I decided to have some "regular" American food so I went to McDonalds to get a Big Mac and fries. As I was still on a pretty limited budget I decided to just get a glass of water to go with it. Well I got the Big Mac and fries and they tasted great. The interesting thing about the experience was that the glass of water that they gave me was hot. Not just room temperature because there was no ice, but rather it was really hot.

http://adage.com/article/global-news/mcdonald-s-opens-virtual-store-push-meals-china/135274/

Come to find out, that is how McDonalds and all the other food places there typically serve their water. If you wanted a cold cup of water they would give you a hot cup of water and a cup of ice so you could cool it down, and would give you a funny look in the process for wanting a cold cup of water. When I had learned enough of the Chinese language, one day I asked some of the people why everyone drinks hot cups of water. They told me that it was healthier to drink hot cups of water than cold cups of water. When I asked why it was healthier they weren't able to give me any real answer other than that was what they had been told since they were young.

https://wiki.geneseo.edu/display/food/Group+16-+Global+reactions+to+McDonalds+and+Other+Fast+Food+Chains

As I continue to learn about hydration and dehydration there does not appear to be a consensus about whether there is an optimal water (or drink) temperature for rehydration. Here are a couple of the ideas/lines of thought I have found in regards to water temperature and hydration:

• Performance and Body Temperature
• Some people believe that cold water is best as it cools your body down quicker. There are a couple studies out there that land on both sides of this issue. A study in 2007 by the University of Exeter (in England) found that water temperature had no effect on preventing the body temperature to rise or improve performance. Another study by the Medicine and Science in Sports and Exercise (2008) found that drinking cold water before and during activities reduced physiological strain on the body (including heat related strain) and led to improved performance. Other studies have suggested that water temperature can cause a change in skin temperature but not in core body temperature. So depending on the study you read you get a different answer.
• Absorbing Rate
• Some studies and research indicate that cold water is absorbed by the stomach quicker than warm water, meaning that your body is absorbing it quicker. 
• Burn More Calories:
• One interesting debate over water temperature is whether drinking cold water causes you to burn more calories today. Some people claim (although I have yet to find a study or any research to back it up) that if you drink cold water you will burn more calories. They argue that your body has to warm the water to body temperature in order to digest it so your body burn about 100 calories a day in warming up cold water. This would be great if it were true as it would be an easy way to burn calories, but I'm not convinced it isn't just wishful thinking.

There are several other debates surrounding the temperature of water you should drink to stay hydrated. While it appears that there is yet to be a general consensus on most of the debates, there is one general issue that everyone seems to agree on, do whatever works for you. The most important thing is to stay hydrated. If you like warm water and you'll drink more that way then do that (I personally never got use to it), and if you enjoy a cold refreshing glass of water during a workout do that. Just make sure to stay hydrated.